Braiins' own history puts the start in 2011: "Jan Capek and Pavel Moravec began their own embedded software company, and so Braiins came to be." The Czech commercial register backs it. Braiins Systems s.r.o., registration number 24147931, was entered on 1 September 2011 at the Municipal Court in Prague, and the register records Čapek as one of its two first managing directors, a position he holds again in the current record.
By the company's account, he and Moravec took over development and operation of the bitcoin mining pool founded by Marek Palatinus, acquired a majority share in 2013, and bought out the remaining stake in 2020.
His most visible technical work is protocol design. Braiins states that Stratum V2 "was developed in 2019 by the Braiins founders Pavel Moravec and Jan Čapek, in collaboration with Matt Corallo and other industry experts". The protocol's headline change is that it lets miners, rather than pools, choose which transactions go into the blocks they work on.